Ruminal and total tract digestibilities in steers fed diets containing liquefied or prilled saturated fatty acids

We studied the effects of the addition of liquefied vs prilled mostly satur ated fatty acids (FA) to the concentrate portion of total mixed diets an ru minal and total tract digestibilities. Four Holstein steers (270 +/- 23 kg) fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin squar e design with 21-d periods. Diets contained (DM: basis) 30.0% corn silage, 22.2% chopped alfalfa hay, 25.0% ground shelled earn, 12.5% soybean meal, a nd 5% of one of the following fat sources: 1) prilled FA (PFA), 2) choice w hite grease (triglycerides) added in liquid form (LTG), 3) 2.5% PFA + 2.5% LTG, or 4) 2.5% liquefied PFA(LFA) + 2.5% LTG. Ad libitum OM intake was not different (P > .10) among diets (mean 7.8 kg/d). Ruminal digestibilities o f OM (35.7, 39.9, 42.2, and 37.3% for Diets 1 to 4, respectively) were grea test (P < .10) for the combination of PFA + LTG and lowest for PFA alone. R uminal digestibilities of NDF, ADF, and starch did not, differ(P > .10) amo ng diets. Total tract digestibilities of OM, NDF, and ADF were greater (P < .10) for the diet containing LTG alone than for the diet containing LFA LTG because of trends for greater postruminal digestibilities. The LFA + LT G diet resulted in a greater proportion of acetate and lower proportion of propionate in ruminal fluid than PPA alone (P < .10). The acetate:propionat e ratio (3.53, 2.96, 3.10, and 2.89 for Diets 1 to 4, respectively) was low er (P < .05) for LFA + LTG or LTG alone than for PFA alone. Postruminal and total tract digestibilities of total FA (66.0, 76.0, 71.2, and 68.9% for D iets 1 to 4, respectively) were lower (P < .05) for PFA than for other diet s. Addition of saturated FA in liquid form resulted in digestibilities and ruminal effects similar to the same saturated FA added in prilled form.